1. Field of the Invention
This invention relates to a paper roll holder for a printer, and, more particularly, to a mechanism allowing the paper roll to be either snapped into place between bearing members or dropped into place within the holder.
2. Summary of the Background Art
Many printers, especially the small point-of-sale printers used to generate sales receipts, use roll paper to achieve the advantages of easy loading, reliable feeding, and of an ability to generate receipts that vary greatly from one another in length. Some such printers provide for snap-in loading of the paper roll, in which a cylindrical center portion of the paper roll is held to rotate between a pair of spring-loaded bearing members. Other such printers provide for drop-in loading, in which the paper roll is dropped into a cavity or bucket that holds the roll by its periphery as the roll rotates. As paper is pulled from the roll during the printing process, the roll rotates within the cavity, being supported by rollers or by a curved surface within the cavity.
A printer configured for holding a snap-in paper roll is described, for example, in U.S. Pat. No. 6,536,606, with the paper roll being held between two inwardly spring loaded spherical bearing members. Spring loaded bearing members having spherical contact surfaces are also used in other applications, such as holding toilet paper or paper toweling, as described in U.S. Pat. No. 4,614,312, and for holding a roll of photographic film within a camera, as described in U.S. Pat. No. 1,402,167. Within a printing device or copier, a paper roll having a cylindrical core may alternately be held by means of spring loaded bearing members having truncated conical surfaces, as described in U.S. Pat. No. 4,821,974, or a paper roll may be held between flanges mounted on a shaft having tapered shafts fitting into cup-shaped holders as described in U.S. Pat. No. 4,821,974. Spring-loading may be accomplished by placing springs at each of the bearing members or at only one of the bearing members. Spherical bearing members have an advantage of allowing the roll to be snapped into place with a straight movement into the holder, with the use of springs at both ends reducing the amount of movement required and centering the paper roll.
U.S. Pat. No. 5,060,877 describes an automatic version of drop-in loading, in which the paper roll, having been dropped into place atop rollers within a cavity, is caused to rotate by spinning the rollers, so that the end paper web is automatically fed into a channel from the roll.
Some users of point-of-sale printers prefer drop-in paper roll loading, because of its inherent simplicity and because of the speed with which it can be accomplished. Other users favor snap-in loading because the paper roll is aligned more accurately within the printer. Therefore, what is needed is a paper roll holder that can be easily converted between snap-in loading and drop-in loading.